Rapid and simple detection of sodium thiocyanate in milk using surface‐enhanced Raman spectroscopy based on silver aggregates

Surface‐enhanced Raman spectroscopy (SERS) was used for rapid detection of sodium thiocyanate in milk employing silver aggregates as active substrate. Silver nanoparticles were induced to silver aggregates by trichloroacetic acid (TCA). The limit of detection (LOD) for sodium thiocyanate was 10⁻² µg ml⁻¹ in water with an analytical enhancement factor of 5.4 × 10⁶. The silver aggregates represent good reproducibility and stability. Good linear relationship was obtained for sodium thiocyanate in milk at concentration ranges from 0.1 to 10 µg ml⁻¹ (R² = 0.995). Using TCA as protein precipitator, silver colloid would aggregate spontaneously when mixing with samples during SERS measurement without the need of additional aggregating agent. The simple pretreatment procedures and analytical methods are less time consuming (<10 min) and environmentally friendly, making the proposed method much practical for in situ detection of sodium thiocyanate in market milk. Copyright © 2014 John Wiley & Sons, Ltd.     

Conductometric and fluorometric studies of sodium dodecyl sulphate in aqueous solution and in the presence of amino acids

The critical micelle concentration (CMC) of sodium dodecyl sulphate (SDS) in pure water and in the presence of amino acids (0.01, 0.02 and 0.03 mol kg^?1), L-valine (Val) and L-leucine (Leu) was determined from conductometric and fluorometric methods using pyrene as luminescence probe. Depression in the CMC at low concentration of amino acids is attributed to the increased hydrophobic–hydrophobic interaction between the non-polar groups of the surfactant, while, at high concentration, amino acids bind strongly with the anion, DS^?, head groups of SDS, thereby, delaying the micelle formation, resulting in increased CMC. A pronounced decrease in the CMC, while a marked increase in λ⁰₊, with decrease in the solvated radius (rather than crystal radius) of the counterions is observed. Negative values of ΔG⁰_m and ΔH⁰_m indicate that micellisation of SDS in the presence of amino acids is thermodynamically spontaneous and exothermic. Highest negative value of ΔH⁰_m in 0.01 m Val, with lowest CMC value, shows that 0.01 m aqueous Val is the most suitable medium favouring the micellisation of SDS. Decrease in I₁/I₃ from Val to Leu confirms the relative hydrophobicity of two amino acids. The observed values of the packing parameter, P, of SDS in water and in aqueous amino acids suggest that micelles formed are spherical in nature.     

Degradation of diclofenac sodium using combined processes based on hydrodynamic cavitation and heterogeneous photocatalysis

Diclofenac sodium, a widely detected pharmaceutical drug in wastewater samples, has been selected as a model pollutant for degradation using novel combined approach of hydrodynamic cavitation and heterogeneous photocatalysis. A slit venturi has been used as cavitating device in the hydrodynamic cavitation reactor. The effect of various operating parameters such as inlet fluid pressure (2–4 bar) and initial pH of the solution (4–7.5) on the extent of degradation have been studied. The maximum extent of degradation of diclofenac sodium was obtained at inlet fluid pressure of 3 bar and initial pH as 4 using hydrodynamic cavitation alone. The loadings of TiO₂ and H₂O₂ have been optimised to maximise the extent of degradation of diclofenac sodium. Kinetic study revealed that the degradation of diclofenac sodium fitted first order kinetics over the selected range of operating protocols. It has been observed that combination of hydrodynamic cavitation with UV, UV/TiO₂ and UV/TiO₂/H₂O₂ results in enhanced extents of degradation as compared to the individual schemes. The maximum extent of degradation as 95% with 76% reduction in TOC has been observed using hydrodynamic cavitation in conjunction with UV/TiO₂/H₂O₂ under the optimised operating conditions. The diclofenac sodium degradation byproducts have been identified using LC/MS analysis.     

铝在氢氧化钠溶液中的电解加工与钝化机理

采用电解腐蚀装置,研究铝芯轴在1mol/L的氢氧化钠溶液中4~28V电压条件下的电流随时间的变化,得到电压与稳定时刻电流的关系曲线。通过改变电解液温度(20~35℃),对数据拟合后得到活化能。当电压高于28V时,铝表面完全钝化,采用扫描电子显微镜得到未钝化样品和钝化样品的表面形貌,采用X射线衍射仪对未钝化样品和钝化样品进行分析表征,得出了钝化样品表面钝化层的主要成分为三羟铝石。从钝化产物的主要成分,推断出表面反应过程及钝化机理。     

光谱法研究ZnO量子点与头孢哌酮钠的相互作用

本文采用均匀沉淀法,在室温条件下,合成了较为稳定的ZnO量子点。用荧光光谱法、紫外可见分光光度法分析了ZnO量子点与头孢哌酮的相互作用,用Stern-Volmer方程研究了头孢哌酮对ZnO量子点的荧光猝灭作用,结果表明属于静态荧光猝灭,计算了不同温度时的猝灭常数(292K:9.550×103 L·mol-1、303K:5.980×103 L·mol-1、313K:4.412×103 L·mol-1)和热力学参数,证明二者主要以范德华作用和氢键作用力结合。根据Forster的偶极-偶极非辐射能量转移原理计算出结合位置距离色氨酸残基2.47nm,发生分子内的非辐射能量转移。为探讨纳米颗粒与此类药物分子之间相互作用的化学机理提供了重要的信息。     

33 W quasi-continuous-wave narrow-band sodium D_(2a) laser by sum-frequency generation in LBO

We demonstrate an all-solid quasi-continuous-wave （QCW） narrow-band source tunable to sodium D2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal. The 1064 nm and 1319 nm lasers are produced from two diode side-pumped Nd：YAG master oscillator power amplifier （MOPA） laser systems, respectively. A 33 W output of 589 nm laser is obtained with beam quality factor M^2 = 1.25, frequency stability better than ±0.2 GHz and linewidth less than 0.44 GHz. A prototype 589 nm laser system is assembled, and a sodium laser guided star has been successfully observed in the field test.     

Leaching of Celestite with Sodium Sulfide

Leaching of celestite mineral, SrSO₄, with sodium sulfide, Na₂S, was investigated from the point of strontium carbonate, SrCO₃, production. Experiments were carried out to explain the conversion mechanism of celestite to strontium disulfide, SrS₂, in Na₂S solution. Effects of stirring speed, particle size, and concentration of Na₂S on conversion were studied at constant temperature and solid‐to‐liquid ratio. The results showed that the rate of conversion mainly depends on Na₂S concentration. It was concluded that leaching of celestite in Na₂S solution for conversion to SrS₂ is possible but slow.     

A Study of the Solubilization of Polar Oily Materials by Alkyl Polyglucoside and Sodium Dodecyl Sulfate in Mixed Surfactant System

The effects of different alkyl chains of nonionic surfactants and solubilized polar oily material on the solubilizing capacity of binary anionic‐nonionic mixed surfactant systems were studied. This system includes surface tension measurements to determine the critical micelle concentration. Results were analyzed using regular solution theory to obtain the mixed micelle and the interaction parameter β, in order to evaluate the type of interactions of surfactants in the mixed micelle. Solubilizing capacity has been investigated by measuring the optical density of solubilized polar oily materials like octanol, decanol, and dodecanol. The solubilizing phenomenon exhibited by mixed surfactants systems showed better results than that of the individual surfactant system. The amount of solubilization in mixed surfactant increases with increase in carbon chain length of alkyl polyglucoside.     

The Kinetics and Mechanism of Ligand Substitution Reaction of Aquapentacyanoruthenate(II) with Nitroso-R-salt and α-Nitroso-β-Naphthol in Presence of Anionic Surfactant Micelle

The kinetics and mechanism of ligand substitution reaction of coordinated water in complex, [Ru(CN)₅H₂O]^3? by two incoming naphthalene substituted ligands [Lⁿ], that is, Lⁿ = nitroso-R-salt (NRS) and α-nitroso-β-naphthol (αNβN) have been studied spectrophotometrically by following an increase in absorbance at λ_max = 525 nm in aqueous medium in presence of anionic surfactant micelle, sodium dodecyl sulphate (SDS) at 25.0 ± 0.1°C as a function of pH, [nitro-R-salt], [α-nitroso-β-naphthol], [Ru(CN)₅H₂O^3?], [SDS] and ionic strength(I) under pseudo-first-order conditions by taking excess [L]. The values of pseudo-first-order rate constants (k_obs) were evaluated from the slope of ln(A_∞ ? A_t) versus time plots for each variation. Both systems were found to follow a dissociative mechanism (D), through the formation of an intermediate, [Ru(CN)₅]^3?. The activation parameters, that is, enthalpy of activation (ΔH^≠) and entropy of activation (ΔS^≠) were computed from the slope and intercept of ln(k_f/T) versus (1/T) plot, which support the proposed mechanistic scheme.     

Entrapment Efficiency of All-trans Retinoic Acid in Surfactant Vesicles

Spontaneous vesicles of dicetyl dimethyl ammonium chloride (DCDAC) and its mixture with sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) are observed respectively in ethanol-water mixed solvents, which have been demonstrated by negative-staining transmission electric microscope (TEM) and atomic force microscope (AFM). Ethanol can promote the vesicle formation, especially to pure DCDAC surfactant system. The entrapment efficiency of the vesicles to all-trans retinoic acid (ATRA) was measured by the first order derivative spectrophotometry method. The entrapment efficiency of ATRA reaches 22% in 0.5 ethanol volume ratio solution when the concentration of DCDAC is 2.5 × 10^?3 mol/L. In the same solvents, the entrapment efficiency could be as high as 62% in 1:9 (molar ratio) DCDAC/AOT mixtures when the total concentration of surfactants is 3.0 × 10^?3 mol/L.